{"oa":1,"external_id":{"arxiv":["2508.21708"]},"date_updated":"2026-05-21T06:16:04Z","department":[{"_id":"JoMa"}],"publication":"Monthly Notices of the Royal Astronomical Society","volume":548,"DOAJ_listed":"1","article_type":"original","month":"05","intvolume":"       548","_id":"21898","abstract":[{"text":"We investigate the nature and spectroscopic diversity of early galaxies from a sample of 41 sources at $z\\geqslant 10$ with James Webb Space Telescope (JWST)/NIRSpec prism observations. We compare the properties of strong ultraviolet (UV) line emitters, traced by intense C iv emission, with those of more ‘typical’ sources with weak or undetected C iv. The more typical (or ‘C iv-weak’) sources reveal significant scatter in their C iii] line strengths, UV continuum slopes, and physical sizes, spanning C iii] equivalent widths (EWs) of $\\sim$1–51 Å, UV slopes of $\\beta \\sim -1.6$ to $-2.6$, and half-light radii of $\\sim$50–1000 pc. In contrast, C iv-strong sources occupy the tail of these distributions, with C iii] EWs of 16–51 Å, UV slopes $\\beta \\lesssim -2.5$, compact morphologies ($r_{\\rm 50} \\lesssim 100$ pc), and elevated star formation surface densities ($\\Sigma _{\\rm SFR} \\gtrsim 100\\, M_\\odot \\, \\mathrm{yr}^{-1}\\, \\mathrm{kpc}^{-2}$). These properties suggest concentrated starbursts that temporarily outshine the host galaxy. Comparing average properties from composite spectra, we find the diversity of the sample is primarily driven by bursty star formation on very short time-scales ($\\le$3 Myr), with strong C iv emitters observed at the apex of the bursts and sources devoid of emission lines during relative inactivity. An apparent association between strong C iv and enhanced nitrogen abundance suggests both may be modulated by the same duty cycle, reflecting a generic mode of star formation. We show that active galactic nuclei are unlikely to contribute significantly to this duty cycle based on UV line diagnostics and photoionization models. Our results support a picture whereby brief bursts and lulls can explain the spectral diversity and early growth of bright galaxies in the first 500 Myr.","lang":"eng"}],"file":[{"content_type":"application/pdf","success":1,"date_created":"2026-05-21T06:14:23Z","file_size":3539140,"file_id":"21902","checksum":"b8f52c6fc5e06b3a505310e7d5898ecf","creator":"dernst","file_name":"2026_MNRAS_RobertsBorsani.pdf","date_updated":"2026-05-21T06:14:23Z","access_level":"open_access","relation":"main_file"}],"quality_controlled":"1","PlanS_conform":"1","OA_type":"gold","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","citation":{"ieee":"G. Roberts-Borsani <i>et al.</i>, “JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 548, no. 3. Oxford University Press, 2026.","mla":"Roberts-Borsani, Guido, et al. “JWST Spectroscopic Insights into the Diversity of Galaxies in the First 500 Myr: Short-Lived Snapshots along a Common Evolutionary Pathway.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 548, no. 3, stag701, Oxford University Press, 2026, doi:<a href=\"https://doi.org/10.1093/mnras/stag701\">10.1093/mnras/stag701</a>.","ista":"Roberts-Borsani G, Oesch PA, Ellis R, Weibel A, Giovinazzo E, Bouwens R, Dayal P, Fontana A, Heintz KE, Matthee JJ, Meyer RA, Pentericci L, Shapley A, Tacchella S, Treu T, Walter F, Atek H, Bose S, Castellano M, Fudamoto Y, Morishita T, Naidu RP, Sanders RL, van der Wel A. 2026. JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway. Monthly Notices of the Royal Astronomical Society. 548(3), stag701.","apa":"Roberts-Borsani, G., Oesch, P. A., Ellis, R., Weibel, A., Giovinazzo, E., Bouwens, R., … van der Wel, A. (2026). JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press. <a href=\"https://doi.org/10.1093/mnras/stag701\">https://doi.org/10.1093/mnras/stag701</a>","chicago":"Roberts-Borsani, Guido, Pascal A Oesch, Richard Ellis, Andrea Weibel, Emma Giovinazzo, Rychard Bouwens, Pratika Dayal, et al. “JWST Spectroscopic Insights into the Diversity of Galaxies in the First 500 Myr: Short-Lived Snapshots along a Common Evolutionary Pathway.” <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press, 2026. <a href=\"https://doi.org/10.1093/mnras/stag701\">https://doi.org/10.1093/mnras/stag701</a>.","ama":"Roberts-Borsani G, Oesch PA, Ellis R, et al. JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway. <i>Monthly Notices of the Royal Astronomical Society</i>. 2026;548(3). doi:<a href=\"https://doi.org/10.1093/mnras/stag701\">10.1093/mnras/stag701</a>","short":"G. Roberts-Borsani, P.A. Oesch, R. Ellis, A. Weibel, E. Giovinazzo, R. Bouwens, P. Dayal, A. Fontana, K.E. Heintz, J.J. Matthee, R.A. Meyer, L. Pentericci, A. Shapley, S. Tacchella, T. Treu, F. Walter, H. Atek, S. Bose, M. Castellano, Y. Fudamoto, T. Morishita, R.P. Naidu, R.L. Sanders, A. van der Wel, Monthly Notices of the Royal Astronomical Society 548 (2026)."},"file_date_updated":"2026-05-21T06:14:23Z","article_number":"stag701","publication_identifier":{"eissn":["1365-2966"],"issn":["0035-8711"]},"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"doi":"10.1093/mnras/stag701","has_accepted_license":"1","issue":"3","date_published":"2026-05-01T00:00:00Z","scopus_import":"1","language":[{"iso":"eng"}],"type":"journal_article","day":"01","ddc":["520"],"oa_version":"Published Version","title":"JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway","article_processing_charge":"Yes","arxiv":1,"OA_place":"publisher","year":"2026","author":[{"last_name":"Roberts-Borsani","full_name":"Roberts-Borsani, Guido","first_name":"Guido"},{"full_name":"Oesch, Pascal A","first_name":"Pascal A","last_name":"Oesch"},{"full_name":"Ellis, Richard","first_name":"Richard","last_name":"Ellis"},{"last_name":"Weibel","full_name":"Weibel, Andrea","first_name":"Andrea"},{"last_name":"Giovinazzo","full_name":"Giovinazzo, Emma","first_name":"Emma"},{"full_name":"Bouwens, Rychard","first_name":"Rychard","last_name":"Bouwens"},{"last_name":"Dayal","full_name":"Dayal, Pratika","first_name":"Pratika"},{"full_name":"Fontana, Adriano","first_name":"Adriano","last_name":"Fontana"},{"full_name":"Heintz, Kasper E","first_name":"Kasper E","last_name":"Heintz"},{"first_name":"Jorryt J","full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","orcid":"0000-0003-2871-127X"},{"full_name":"Meyer, Romain A","first_name":"Romain A","last_name":"Meyer"},{"last_name":"Pentericci","full_name":"Pentericci, Laura","first_name":"Laura"},{"first_name":"Alice","full_name":"Shapley, Alice","last_name":"Shapley"},{"first_name":"Sandro","full_name":"Tacchella, Sandro","last_name":"Tacchella"},{"last_name":"Treu","full_name":"Treu, Tommaso","first_name":"Tommaso"},{"last_name":"Walter","full_name":"Walter, Fabian","first_name":"Fabian"},{"last_name":"Atek","first_name":"Hakim","full_name":"Atek, Hakim"},{"last_name":"Bose","full_name":"Bose, Sownak","first_name":"Sownak"},{"last_name":"Castellano","full_name":"Castellano, Marco","first_name":"Marco"},{"full_name":"Fudamoto, Yoshinobu","first_name":"Yoshinobu","last_name":"Fudamoto"},{"first_name":"Takahiro","full_name":"Morishita, Takahiro","last_name":"Morishita"},{"first_name":"Rohan P","full_name":"Naidu, Rohan P","last_name":"Naidu"},{"first_name":"Ryan L","full_name":"Sanders, Ryan L","last_name":"Sanders"},{"first_name":"Arjen","full_name":"van der Wel, Arjen","last_name":"van der Wel"}],"date_created":"2026-05-20T14:34:29Z","status":"public","acknowledgement":"We thank the anonymous referee for useful and constructive\r\nfeedback that improved the manuscript. GRB is grateful to Vasily\r\nBelokurov and Sarah Kane for providing the relevant abundances\r\nforthe Aurora data in Fig. 11, as well asto Tiger Yu-Yang Hsiao for\r\nhelpful discussions regarding the MACS 0647-JD source. We are\r\nalso grateful to Gabe Brammerfor useful discussions and his continuous efforts in maintaining and improving the msaexp code,\r\nfrom which the high-z community continues to benefit greatly.\r\nLastly, we also thank the numerous teams of the observational\r\nprograms used in this study, for developing these valuable data\r\nsets. The data used in this study are derived from the following\r\nprograms: 1181 (PI Eisenstein; D. J. Eisenstein et al. 2023a), 1210\r\n(PI Luetzgendorf; D. J. Eisenstein et al. 2023a), 1211 (PI Isaak;\r\nM. V. Maseda et al. 2024), 1286 (PI Luetzgendorf; D. J. Eisenstein\r\net al. 2023a), 1287 (PI Isaak; D. J. Eisenstein et al. 2023a), 1345\r\n(PI Finkelstein; S. L. Finkelstein et al. 2025), 1433 (PI Coe; T. Y.-\r\nY. Hsiao et al. 2024a), 2561 (PI Labbé; R. Bezanson et al. 2022),\r\n2750 (PI Arrabal Haro; P. Arrabal Haro et al. 2023b), 3073 (PI\r\nCastellano; M. Castellano et al. 2024), 3215 (PIs Eisenstein &\r\nMaiolino; D. J. Eisenstein et al. 2023b), 5224 (PIs Oesch & Naidu;\r\nOesch et al. in preparation), 6368 (PI Dickinson; V. Kokorev et al.\r\n2025). The authors acknowledge the aforementioned teams and\r\nPIs where development of their observing program(s) was done\r\nwith a zero-exclusive-access period.\r\nThis work is based on observations made with the\r\nNASA/ESA/CSA JWST. The data were obtained from the\r\nMikulski Archive for Space Telescopes at the Space Telescope\r\nScience Institute, which is operated by the Association of\r\nUniversities for Research in Astronomy, Inc., under NASA\r\ncontract NAS 5-03127 for JWST. The specific observations\r\nanalysed can be accessed via DOI 10.17909/jqj3-ws37. Some\r\nof the data products presented herein were retrieved from the\r\nDawn JWST Archive (DJA). DJA is an initiative of the Cosmic\r\nDawn Center (DAWN), which is funded by the Danish National\r\nResearch Foundation under grant DNRF140.\r\nRSE acknowledges generous financial support from the Peter\r\nand Patricia Gruber Foundation. YF acknowledgessupportsfrom\r\nJSPS KAKENHI Grant Numbers JP22K21349 and JP23K13149.\r\nThis work has received funding from the Swiss State Secretariat\r\nfor Education, Research and Innovation (SERI) under contract\r\nnumber MB22.00072, as well as from the Swiss National Science\r\nFoundation (SNSF) through project grant 200020_207349.","publisher":"Oxford University Press","publication_status":"published"}